Tesi sul tema "WLCG"

La Grille de calcul mondiale pour le LHC (WLCG) offre une infrastructure informatique distribuée considérable dédiée à la communauté scientifique impliquée dans le Grand Collisionneur de Hadrons (LHC) du CERN. Avec un stockage total d'environ un exaoctet, le WLCG répond aux besoins de traitement et de stockage des données de milliers de scientifiques internationaux. À mesure que la phase du High-Luminosity LHC (HL-LHC) approche, le volume de données à analyser augmentera considérablement, dépassant les gains attendus grâce à l'avancement de la technologie de stockage. Par conséquent, de nouvelles approches pour un accès et une gestion efficaces des données, telles que les caches, deviennent essentielles. Cette thèse se plonge dans une exploration exhaustive de l'accès au stockage au sein du WLCG, dans le but d'améliorer le débit scientifique global tout en limitant les coûts. Au cœur de cette recherche se trouve l'analyse des journaux d'accès aux fichiers réels provenant du système de surveillance du WLCG, mettant en évidence les véritables schémas d'utilisation.Dans un contexte scientifique, la mise en cache a des implications profondes. Contrairement à des applications plus commerciales telles que la diffusion de vidéos, les caches de données scientifiques traitent des tailles de fichiers variables, allant de quelques octets à plusieurs téraoctets. De plus, les associations logiques inhérentes entre les fichiers influencent considérablement les schémas d'accès des utilisateurs. La recherche traditionnelle sur la mise en cache s'est principalement concentrée sur des tailles de fichiers uniformes et des modèles de référence indépendants. Au contraire, les charges de travail scientifiques rencontrent des variations de taille de fichier, et les interconnexions logiques entre les fichiers influencent de manière significative les schémas d'accès des utilisateurs.Mes investigations montrent comment l'organisation hiérarchique des données du LHC, en particulier leur compartimentation en "datasets", influence les schémas de demande. Reconnaissant cette opportunité, j'introduis des algorithmes de mise en cache innovants qui mettent l'accent sur la connaissance spécifique des datasets et je compare leur efficacité avec les stratégies traditionnelles axées sur les fichiers. De plus, mes découvertes mettent en évidence le phénomène des "hits retardés" déclenché par une connectivité limitée entre les sites de calcul et de stockage, mettant en lumière ses répercussions potentielles sur l'efficacité de la mise en cache.Reconnaissant le défi de longue date que représente la prédiction de la Popularité des Données dans la communauté de la Physique des Hautes Énergies (PHE), en particulier avec les énigmes de stockage à l'approche de l'ère du HL-LHC, ma recherche intègre des outils de Machine Learning (ML). Plus précisément, j'utilise l'algorithme Random Forest, connu pour sa pertinence dans le traitement des Big Data. En utilisant le ML pour prédire les futurs schémas de réutilisation des fichiers, je présente une méthode en deux étapes pour informer les politiques d'éviction de cache. Cette stratégie combine la puissance de l'analyse prédictive et des algorithmes établis d'éviction de cache, créant ainsi un système de mise en cache plus résilient pour le WLCG.En conclusion, cette recherche souligne l'importance de services de stockage robustes, suggérant une orientation vers des caches sans état pour les petits sites afin d'alléger les exigences complexes de gestion de stockage et d'ouvrir la voie à un niveau supplémentaire dans la hiérarchie de stockage. À travers cette thèse, je vise à naviguer à travers les défis et les complexités du stockage et de la récupération de données, élaborant des méthodes plus efficaces qui résonnent avec les besoins évolutifs du WLCG et de sa communauté mondiale
The Worldwide LHC Computing Grid (WLCG) offers an extensive distributed computing infrastructure dedicated to the scientific community involved with CERN's Large Hadron Collider (LHC). With storage that totals roughly an exabyte, the WLCG addresses the data processing and storage requirements of thousands of international scientists. As the High-Luminosity LHC phase approaches, the volume of data to be analysed will increase steeply, outpacing the expected gain through the advancement of storage technology. Therefore, new approaches to effective data access and management, such as caches, become essential. This thesis delves into a comprehensive exploration of storage access within the WLCG, aiming to enhance the aggregate science throughput while limiting the cost. Central to this research is the analysis of real file access logs sourced from the WLCG monitoring system, highlighting genuine usage patterns.In a scientific setting, caching has profound implications. Unlike more commercial applications such as video streaming, scientific data caches deal with varying file sizes—from a mere few bytes to multiple terabytes. Moreover, the inherent logical associations between files considerably influence user access patterns. Traditional caching research has predominantly revolved around uniform file sizes and independent reference models. Contrarily, scientific workloads encounter variances in file sizes, and logical file interconnections significantly influence user access patterns.My investigations show how LHC's hierarchical data organization, particularly its compartmentalization into datasets, impacts request patterns. Recognizing the opportunity, I introduce innovative caching policies that emphasize dataset-specific knowledge, and compare their effectiveness with traditional file-centric strategies. Furthermore, my findings underscore the "delayed hits" phenomenon triggered by limited connectivity between computing and storage locales, shedding light on its potential repercussions for caching efficiency.Acknowledging the long-standing challenge of predicting Data Popularity in the High Energy Physics (HEP) community, especially with the upcoming HL-LHC era's storage conundrums, my research integrates Machine Learning (ML) tools. Specifically, I employ the Random Forest algorithm, known for its suitability with Big Data. By harnessing ML to predict future file reuse patterns, I present a dual-stage method to inform cache eviction policies. This strategy combines the power of predictive analytics and established cache eviction algorithms, thereby devising a more resilient caching system for the WLCG. In conclusion, this research underscores the significance of robust storage services, suggesting a direction towards stateless caches for smaller sites to alleviate complex storage management requirements and open the path to an additional level in the storage hierarchy. Through this thesis, I aim to navigate the challenges and complexities of data storage and retrieval, crafting more efficient methods that resonate with the evolving needs of the WLCG and its global community

Workload Control (WLC) is one of few Production Planning & Control (PPC) solutions appropriate for Make- To-Order (MTO) companies and Small & Medium sized Enterprises (SMEs), yet its successful implementation remains an enduring challenge. Much research attention has focused on developing the concept in a theoretical or simulation context; relatively little has focused on implementing the concept in practice, and more empirical evidence is needed on successful implementations. Of the few successful WLC implementations which have been published previously, the focus has been on the result of implementation while the process of implementation itself is still a 'black box'. Where more detail on the implementation process has been given in previous studies, evidence of effectiveness in practice has not been provided. To address this research gap, this thesis presents a successful implementation of a comprehensive WLC approach through action research; this is the first study which demonstrates the impact of WLC on performance in practice alongside a detailed account of the implementation process. Performance improvements observed include: reduced lead times; improvements in lateness and tardiness; reduced costs; improved internal and external co-ordination; and higher quality. In addition to details of this successful implementation, a wider body of evidence on the characteristics of MTO SMEs that affect WLC implementation has been obtained through a survey of 41 companies using semi-structured face-to-face interviews. This compensates for the limitation of a single case and adds an element of generality to the research findings. Thus, a generalised set of WLC specific implementation issues and an implementation strategy for the widespread adoption of WLC in practice has been developed.

Make-to-order and engineer-to-order companies often have few standard products and a demand that is hard to predict. To get orders the company gives quotations and competes for the customers. This thesis aims to identify the factors contribution to the lead time uncertainty at make-to-order companies and then to suggest a methodology to handle or eliminate some of these factors. A case study was conducted at a medium sized company with a combined make-to-order and engineer-to-order manual production system. The company has long lead times in the order process as well as the assembly process. The lead times for the case company are measured in weeks rather than minutes, hours or days. Information was collected during a three month period through interviews with the employees, attendance in meeting and observations at the shop floor. The information was structured and analyzed using for example anity diagrams, inter-relationship digraphs and a mini risk assessment. A solution was chosen through a matrix diagram, comparing different possible solutions in relation to the identified factors. The investigation showed that the problem area of quoting delivery dates was a significant problem. There is a tendency to give quotations for more than what would be possible to produce, to make sure the company get enough orders. This strategy induce uncertainty to the quoted lead times, since more quotations than what is possible might get accepted and the orders then have to wait for others to be completed. The long lead times further increase the problem, since the impact from the quotation phase is not visible until months later. Many times the company end up with too many orders to full and a stressful environment on the shop floor. The proposed improvements are based on the workload control approach and the two decision points; Customer Enquiry & Order stage and the Job Release stage. The goal is for the company to be able to make well informed and motivated planning decisions where priorities are applied in a systematic way. Focus should therefore be on improving the communication between departments. One important step is visualising the capacity utilisation when looking for a new delivery date. The quoted orders should be taken into account since they imply a contingent demand and use of capacity. The expected outcome of the methodology is that the quoted lead times will be more accurate and the company will have better means to deliver on time.
Företag som jobbar enligt tillverkning-mot-order och utveckling-mot-order har ofta få standardprodukter och en efterfragan som är svår att forutsäga. För att fåbeställningar skickar företaget offerter och konkurrerar om kunderna. Uppsatsen syftar till att identiera de faktorer som bidrar till osäkerhet i ledtiden hos tillverkning-mot-order-företag och sedan föreslå en metod för att hantera eller eliminera några av dessa faktorer. En fallstudie genomfördes på ett medelstort finmekanikföretag som kombinerar tillverkning-mot-order och utveckling-mot-order i ett manuellt produktionssystem. Företaget har långa ledtider i både orderprocessen och monteringen. Ledtiderna hos företaget mäts i veckor snarare än minuter, timmar eller dagar. Information samlades in under en tremånadersperiod genom intervjuer med de anställda, närvaro på möten och observationer av monteringen. Informationen strukturerades och analyserades med hjälp av till exempel släktskapsdiagram, relationsdiagram och en miniriskanalys. En lösning valdes genom ett matrisdiagram, som jämför olika möjliga lösningar i förhållande till de identifierade faktorerna. Undersökningen visade att offereringen av leveranstider var ett betydande problem. Det finns en tendens att offerera mer än vad som skulle vara möjligt att producera, för att se till att företaget får tillräckligt med beställningar. Denna strategi orsakar osäkerhet i de ledtider som offereras, eftersom fler offerter än vad som är mojligt kan accepteras och beställningar får sedan vänta på att andra ska bli klara. De långa ledtiderna ökar problemet ytterligare, eftersom effekterna från offertfasen inte märks förrän månader senare. Många gånger resulterar det i att företaget har allt för många beställningar att jobba med och en stressig miljö i monteringen. De föreslagna förbättringarna bygger på arbetsbelastningskontroll, med beslutspunkter vid kundförfrågan & beställning samt orderstart i montering. Målet är att företaget ska kunna göra väl underbyggda och motiverade planeringsbeslut där prioriteringar tillämpas på ett systematiskt sätt. Fokus bör därför ligga på att förbättra kommunikationen mellan avdelningarna. Ett viktigt steg är att visualisera kapacitetsutnyttjandet när vi letar efter ett nytt leveransdatum. Även de offerter som skickats ut men ännu inte accepterats bör beaktas eftersom de innebär en eventuell efterfrågan och användning av kapaciteten. Det förväntade resultatet av metoden är att de offererade ledtiderna kommer att vara mer exakt och bolaget kommer att ha bättre möjligheter att leverera i tid.

The aim of this thesis is to deepening the knowledge of the Production Planning and Control System known as Workload Control (WLC). It is commonly recognized that production management techniques such as Just-In-Time (JIT) are not easy to apply in highly complex production environment with low repetitive operations and a very high product variety. In the late '70s, in many countries, researchers have begun to develop and implement methods for order release control, known as ORR systems (Order Review and Release). These methods try to limit the work-in-process level avoiding the need of complex and expensive scheduling software. Although the WLC has been developed since the early 80s, only a handful of successful case studies have been reported so far. This thesis aims to achieve the following objectives: • deepen the theoretical knowledge of some methods and rules that are part of the WLC model applied in a complex system, considering the whole product structure and routings, material flow and distribution of customer orders arrivals. • evaluate the effect and the interaction of various operating parameters and different methods defined within the WLC model on a number of operational performance indicators. • To test the performance of a new order release method that is part of load balancing category. This work, through a simulation approach, examines the parameters which make up the WLC method in an existing manufacturing job shop. The simulation approach allows to test some methods and to change these methods and the parameters’ values without intervening directly in the company. The uniqueness and value of this thesis comes from the complexity of the model developed, which reproduces very closely the manufacturing structure. The size of the experimental plan developed, in terms of number of factors and levels is a further value element. The extension of the experimental plan makes it possible to assess the effects and interactions of many parameters which make up the WLC model. The analysis of experimental data and further analysis of relevant scientific literature, helped to deepen the theoretical knowledge and operational issues concerning the implementation of Workload Control in a complex manufacturing system and identify some possible levers of intervention. Some results depart significantly from those discussed in the literature. This fact is mainly related to the complexity and the likelihood of its model, which is clearly different from those “theoretical” used in simulation studies.
La tesi ha come obiettivo l’approfondimento del sistema di pianificazione e controllo della produzione noto come Workload Control (WLC). Da tempo infatti è stata riconosciuta l’idea che tecniche di gestione della produzione come il Just-In-Time (JIT) non sono di facile applicazione in ambienti fortemente complessi con produzione poco ripetitiva e molto estesa in termini di varietà offerta al cliente. Alla fine degli anni ‘70, in più parti del mondo, i ricercatori hanno iniziato a sviluppare ed implementare alcuni metodi per il rilascio controllato degli ordini, noti come ORR systems (Order Review and Release), che consentissero di limitare il work-in-process in produzione ottenendo un reparto snello, prescindendo dall’utilizzo di complessi e costosi software per schedulazione. Benché il WLC sia stato sviluppato a partire dai primi anni ‘80, fin ora sono state riportate solamente una manciata di casi applicativi di successo. Il progetto di ricerca condotto ha permesso il raggiungimento dei seguenti obiettivi:  approfondire le conoscenze teoriche di funzionamento di alcuni metodi e regole facenti parte del modello WLC in un sistema complesso, considerando integralmente la struttura di prodotto e dei cicli tecnologici, dei flussi di materiali e la distribuzione degli ordini cliente.  valutare l‘effetto e l‘interazione dei vari parametri di funzionamento e delle differenti logiche di WLC definiti all‘interno del modello proposto su alcuni indicatori di prestazione operativi.  Testare le prestazioni di un nuovo metodo di rilascio degli ordini facente parte della categoria del load balancing. Il lavoro di tesi, attraverso un approccio simulativo, esamina i parametri costituenti il metodo WLC in un ambiente manifatturiero esistente di tipo job shop operante con logica to-order. L‘approccio simulativo consente in primo luogo di testare alcune logiche e in secondo luogo di variare tali logiche e i valori dei parametri di funzionamento del modello senza intervenire direttamente in azienda. L‘unicità ed il valore del lavoro di tesi deriva dalla complessità del modello adottato, che riproduce molto fedelmente quello aziendale. Le dimensioni del piano sperimentale sviluppato, in termini di numerosità dei fattori e dei livelli considerati costituisce un ulteriore elemento di pregio. L‘estensione del piano sperimentale consente infatti di valutare gli effetti e le interazioni di molti dei parametri costituenti il modello WLC. Le analisi dei dati sperimentali, nonché un’ulteriore analisi della letteratura scientifica di riferimento, hanno permesso di approfondire le conoscenze teoriche e le problematiche di funzionamento inerenti l’implementazione del Workload Control all’interno di un sistema manifatturiero complesso, e di individuare alcune possibili leve di intervento. Alcuni risultati si discostano fortemente da quanto presente in letteratura; questo fatto è principalmente legato alla complessità e alle verosimiglianza del modello impiegato, che si distingue nettamente da quelli stilizzati di sovente impiegati nelle ricerche di carattere simulativo

Research in sustainable macroalgae aquaculture has been gaining hype (e.g. Seafarm) to provide advancements in new significant sources of food, feed, materials and bio-energy. Despite the fact that in Asia the offshore production of macroalgae is established for many decades, in Europe is still in its infancy. The issue on where to find suitable cultivation areas without conflicting with current uses to respect the environment and the socio-economic activities is a great challenge. This Master of Science thesis aimed to find suitable offshore areas in order to facilitate implementations of macroalgae cultivations in the Swedish West Coast. Thirteen criteria in environmental, economic and social sustainability aspects were identified and employed (e.g. Depth, Distance to Ports, and Natural and Preserved areas (NPAs)), and the tools Geographic Information Systems (GIS) and Multi-criteria Analysis (MCA) were used in the form of GIS-MCDA, an integrated method available in Idrisi. To aggregate the criteria, Boolean and Weighted Linear Combination (WLC) techniques were applied. The results showed that Boolean areas cover 537 km2 (6,98% of the study area). The best suitable areas, possessing the maximum suitability index 10, that resulted from two WLC models comprise 5 km2 (0,07% of the study area) and 26 km2 (0,34% of the study area) including and excluding the criterion NPAs as constraint, respectively. The results further indicated that GIS-MCDA models excelled in providing an overview for effective spatial decision-making. Both techniques play a role in suitability analysis and complement each other in finding an optimal site which could be carefully selected out of the identified areas. It is recommended that areas with a suitability index 10 be chosen inside Boolean suitable areas. Moreover, this study could act as a driving force to build a resilient planning framework that would boost sustainable placement and development of offshore macroalgae cultivations.

Nata dal progetto di migrazione, in un ambiente consolidato, di una infrastruttura Wireless distribuita su territorio all'interno di una MAN (Metropolitan Area Network), si cerca di illustrare quali sono i passi fondamentali da seguire e con cosa ci si deve misurare per progettare una soluzione funzionale ed elaborare una strategia avendo a che fare con architetture complesse, dove la messa in esercizio di un servizio offerto ad un numero elevato di utenti prevede uno studio ben preciso delle attività da svolgere. Un'attenta analisi, ci consentirà di seguire e riadattare le scelte implementative in funzione delle esigenze infrastrutturali, illustrandone le difficoltà, gli imprevisti e le modifiche intraprese passo passo. Gli argomenti trattati tendono a far comprendere con quali problematiche si ha a che fare nella fase implementativa passando dalla fase di analisi a quella decisionale, quella di migrazione architetturale e di installazione, oltre che alla scelta delle componenti e delle tecnologie specifiche che, prima di essere portate a regime, devono essere sottoposte agli opportuni test per la comprensione/risoluzione di problematiche complesse; come le operazioni necessarie per operare con una efficace metodologia.

Workload control (WLC) systems constitute a framework mainly for the inputoutput control systems which regulate both jobs&rsquo
queues into the workshop and the flow of finished goods out of the workshop. This study is concerned with the job entry and release level of WLC which maintains a pool of unreleased jobs for the controlled release of jobs. While most of the studies in WLC concepts deal with the centralized workload control, our study decentralizes the job entry and release control and makes workstations more powerful in schedule decision making. Job&rsquo
s information is sent to the workstations by mediator which is the supervisor of the workstation. Both mediator and work stations are represented by agents in a distributed system. Jobs&rsquo
routing information is assumed to be known in advance. The developed system is verified and validated by means of test runs. Results are analyzed as well.